Several systems have been used to grade and classify bladder neoplasms. The system proposed by the World Health Organization (WHO) in 1972 distinguished papillomas from grades I, II, and III papillary transitional cell carcinomas (TCCs) [1].

In 1998, the WHO and the International Society of Urologic Pathologists (ISUP) published a consensus classification system for urothelial (transitional cell) neoplasms [2]. The clinical significance of this schema was validated by subsequent studies, and in 2004, it was accepted as the standard classification schema [3].

According to this system, urothelial carcinoma is classified as low-grade and high-grade based upon the degree of nuclear anaplasia and architectural abnormalities (figure 1). With rare exceptions (eg, nested or tubular variants), invasive urothelial carcinoma is high grade in its cytological features.

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